Atsuyuki Daido

EFFECTS OF SEDIMENT SUPPLY AND GRAIN SORTING ON LOW-WATERCOURSE FORMATION IN CHANNEL WITH ALTERNATE BARS

Effects of sediment supply and grain sorting on the formation process of low-watercourse in a straight channel with alternate bars are investigated by means of flume tests using uniform and non-uniform sediment. Results are summarized as follows:(1) The low-watercourse is shallow and unstable when the bed level does not vary by sediment supply, whereas the deep and stable low-watercourse is formed when the bed degradation progresses by no sediment supply.(2) The emerged bars in the non-uniform sediment bed are formed with grain sorting, and their upper and lower part mainly consists of coarse grains and fine grains, respectively. These emerged bars are more stable than those in the uniform sediment bed, and contribute to the stability of the low-watercourse.(3) The meandering wavelength of the low-watercourse increases considerably with progression of the bed degradation, and is about 2-3 times the mean wavelength of the alternate bars.

Flow Resistance and Bed Load Transport Rate for Sand Waves

Bed shear stress distribution along the bed surface is derived from boundary layer equation. Then, an effective shear stress for sand waves is expressed as integration of the bed shear stress distribution. As the bed load motion is influenced by fluctuation of flow intensity, the estimation methods of pick-up rate and average step length are proposed by considering these influences. The bed load distribution along a sand wave is calculated by using stochastic model consists of pick-up rate and step length. The results of application to experimental measurements are well good.

Non-Uniform Flow for Mass of Sediment Particle and Extreme Clay Content Liquid

To clear the difference among the liquid, the mass of sediment particle flow andthe extreme content flow of clay, this report treats with the non-uniform flow of those flow. By the energy analysis for those fluid, the normal depth and the critical depth are defined as same as liquid. However, those flow has the non-flow part in the layer, because those fluid has the frictional angle or the yield shear stress.To divide of the non-flow parts, the equilibrium gradient is introduced. The upper parts on the equilibrium gradient which is drown from the behind corner of the obstacle move with the normal depth.